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  <title>Document</title>
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  <script>
    // 21行代码打印20 20 20，是否正确，为什么
    const obj = { count: 10 }
    function fn(x) {
      return this.count + x
    }

    const res1 = fn.call(obj, 10)  
    const res2 = fn.apply(obj, [10]) 
    const res3 = fn.bind(obj, 10) 

    console.log(res1, res2, res3);
  </script>
</body>
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